It is well known to use a tolerance ring to mount a component on a pivot or pin. The component has a bore in it, into which the pivot or pin is received, and the tolerance ring is mounted in the bore, between the pivot or pin and the wall of the bore to act as a link. The tolerance ring provides sufficient rigidity in the connection, but permits the component to move relative to the pivot or pin when excessive loads are applied. Tolerance rings are used, for example, to mount the actuator arm of a hard disk drive onto the pivot assembly for that arm.
However, recent developments in such hard disk drive arrangements have tended to use actuator arms of reduced thickness, thereby reducing the amount of contact between the tolerance ring and the arm. As the thickness of the arm is reduced, so is the axial length of the bore in the arm, and hence, the engagement of the arm by the tolerance ring also reduces, possibly to a point at which the gripping of the arm by the tolerance ring becomes ineffective. In practice, if the arm has a thickness of less than 3 mm, the normal arrangements for mounting an actuator arm onto its pivot assembly via a tolerance ring made be unsuccessful.
FIG. 1 of the accompanying drawings illustrates the mounting of a conventional actuator arm for a hard disk drive. The arm 10 has a bore 11 therein into which is received a pivot assembly 12. The pivot assembly 12 is mounted on a suitable mounting (not shown) to enable to actuator arm to move relative to the hard disk(s) of the drive. In the arrangement of the FIG. 1, the arm 10 is intended for use with 3 disks, and the arm 10 divides into three heads 13 at its end, which will move proximate respective disks (not shown) of the drive.
As illustrated in FIG. 1, there is a tolerance ring 14 which is mounted on the pivot assembly 12, which will engage the walls of the bore 11. The tolerance ring 14 has ridges 15 thereon which will grip the wall of the bore 11. Because there are multiple heads 3, the bore 11 has sufficient axial length for the gripping by the tolerance ring 14 to be sufficient to hold the arm 10 in place on the pivot assembly, at least for the normal range of forces that are applied to the arm.
However, as the capacity of hard disks is reduced, there is less need for multiple heads and disks in a hard disk drive, and thus the thickness of the arm 10 may be reduced. The axial length of the bore 11 may then be insufficient provides suitable gripping by the tolerance ring 14.
It has been suggested that other arrangements may be used to fix the arm of a hard disk drive onto the pivot assembly. Thus, as illustrated in FIG. 2 the arm 10 may be held onto the pivot assembly 12 by a clip 20. Alternatively, adhesive 21 may be applied between the arm 10 and the pivot assembly 12, as in FIG. 3. However, such arrangements are not satisfactory, because the arrangement of FIG. 2 may not provide sufficient radial stiffness, and the use of adhesive as in FIG. 3 makes manufacturing more difficult.